Wastewater Treatment Plant

The Wastewater Treatment Plant was recently upgraded in 2020 from a lagoon treatment facility to a 4-Stage Bardenpho process that removes nitrogen.  The new treatment plant facility upgrade also included upgrades to the Main Pump Station, installation of dual force sewer mains, and a septage receiving station.  The total cost of all the upgrades was $53.5 million.

Exeter has a National Pollutant Discharge Elimination System (NPDES) Permit that regulates what can be discharged into the Squamscott River.  The driving factor of the treatment plant upgrade was the permitted total nitrogen limit which currently requires a seasonal nitrogen discharge to an interim level of 8 mg/L, to an eventual 5 mg/L.  The former lagoon system was unable to remove nitrogen down to these levels.  Exeter has made a profound investment to protecting the environment, Great Bay specifically.  A new draft permit for total nitrogen discharge levels will potentially be given to the Town of Exeter, as well as the 12 other communities that discharge to Great Bay, in the year 2020.  The new treatment facility is running well and operational changes continue to be made to optimize the process to get the best treatment possible.

Waste Disposal Warning

The NHDES has asked us to share the following information and observations regarding wastewater treatment:

Private septic and municipal wastewater treatment systems are experiencing clogging and failure as a result of non-flushable materials being used. Anecdotally, disposing of larger amounts of disinfectants appears to be upsetting private septic systems. Please share with your colleagues and customers that disposal of non-flushables and excess disinfectants should be avoided.

AWARD Winning Wastewater Treatment Plant 2021

The Town of Exeter Wastewater Treatment Plant is the recipient of the USEPA Region 1 2021 Regional Wastewater Treatment Plant Operation and Maintenance Excellence. This award covers the USEPA Region 1 area, which includes all the New England states (CT, MA, ME, NH, RI & VT). There was one other recipient of this award from Maine.

During Senator Shaheen's visit, Tracy Wood, Administrator for the NHDES Wastewater Engineering Bureau, made the nomination to USEPA. She recognized the significant efforts the Town has put forth, from the proper planning and design to the multiple capital projects that have paved the way for the construction and success of the plant. And the support of the Exeter community and voters have been a key piece of all of that.

Official letter from NHDES can be found below within supporting documents.

EnviroMix's Operational Excellence Award 2023

In 2017, the Town of Exeter, New Hampshire, began construction of a new wastewater treatment facility to replace an antiquated lagoon process. To meet the stringent seasonal total nitrogen limit of 5 mg/l, the new facility integrated a four-stage Bardenpho process for enhanced nitrogen removal. EnviroMix’s BioMix Compressed Gas Mixing System was selected for the following applications: first stage anoxic, anoxic swing, mixing limited aeration, second stage anoxic, and aerated sludge holding.

“Supervisor Chris Goodwin and his team take a lot of pride in their facility, expertly operating their BioMix system in order to meet stringent nitrogen limits,” stated Scott Mulinix, EnviroMix director of regional sales. “We’re honored to partner with the plant in their commitment to excellence and to support the energy efficient, environmentally friendly solution they provide the town of Exeter.”

BioMix was selected for numerous reasons:

The system offered 20% lower energy consumption than hyperbolic mixers. BioMix operates independently from or concurrently with aeration to provide anoxic mixing or supplemental mixing in the swing zones. It also allows decoupling of aeration from mixing in the aerated sludge holding tanks.

BioMix was seamlessly integrated into the mixed zones and sludge holding tanks, improving the design, reducing the cost, and increasing the performance of the aeration system. 

The centralized compressor system simplifies maintenance by replacing 16 mechanical mixers while still meeting the total process demand. 

BioMix provides Exeter annual O&M cost savings of $25,000 and 20-year net present worth savings of over $535,000 versus hyperbolic mixers. Implementation of BioMix in the new four-stage process has reduced the nitrogen load by more than 100 tons per year.